UDMA66 = UDMA 4?

I've got an Abit BE6-2 motherboard with a HPT366 BIOS UDMA controller on it.  I have to set the device mode for my new IBM Ultra66 drive, but it shows now option for a UDMA66... I can choose one of the following:
UDMA 0
UDMA 1
UDMA 2
UDMA 3
UDMA 4
PIO 0
PIO 1
PIO 2
PIO 3
PIO 4
MW DMA 0
MW DMA 1
MW DMA 2

What is MW DMA and what UDMA mode is appropriate for my Ultra66 drive?
Thanks-

 Jeremy


j-enosAsked:
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MrbreezeConnect With a Mentor Commented:
Jeremy,
There is a lot of names for the same thing. Different manufacturers call it by different names but it is all the same. MW DMA is Multi-Word DMA and it is the same as UDMA. You need to set your Ultra/66 drive on UDMA mode 4.
                          Mrbreeze
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j-enosAuthor Commented:
Thanks-  you at least gave me something to use.  But under what conditions would I use MW DMA... or UDMA 3?
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MrbreezeCommented:
jeremy,
As I said the names are different but the technology is the same. DMA allows the drive to use Direct Memory Access. That makes the drives able to transfer faster. The process to do so is called Multi Word Direct Memory Access. All DMA drives no matter what they are called are MW DMA. Each level is faster than the other.
The first is PIO 0. It is the same as MW DMA 0 and UDMA 0.
You would use the slower modes for compatibility with other slower components like motherboards, processors and the like. Most all boards made in the past few years can handle UDMA 2 which is 33mbs. Your drive is 66mbs so it is UDMA 4.
So you asked
"But under what conditions would I use MW DMA... or UDMA 3" and the answer is to meet the abilities of your machine. The drive you have could be used on older machines that are slower and you would use a slower UDMA mode to compensate. A good example is if you used the Ultra/66 drive to give data to a CDRW drive that could only use UDMA 2. Your drive would have to wait on the CDRW because it is faster.
Does that help answer your question. That was a lot for a "D" grade huh?  hehehe
                           Mrbreeze
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j-enosAuthor Commented:
Sorry for the "D"...  I just didn't want to reject the answer because it did get me on the road.  But things still don't make sense.  The options I listed in the question were each exclusive of the others.  If MW DMA 0 and UDMA 0 and PIO 0 are all the same, why are they different options.  Also, it is clear that I would slow down the UDMA for certain drive relationships, but that doesn't explain at all what UDMA 3 would be.
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MrbreezeCommented:
Jeremy,
I am to blame for the confusion because I stated that they are all the same thing with different names when in fact they are different though some of them carry the same transfer rates. Each of the modes use different interfaces to transfer data and it would be best for me to give you a link to a site that explains all of it in detail and you can get a better understanding.

http://www.pcguide.com/ref/mbsys/res/dma/index.htm
Check this out and I'll just keep my "D"
                             Mrbreeze
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j-enosAuthor Commented:
Just got a reply from Highpoint...  Just thought I'd paste it up here.

            Jeremy


Set UDMA66 drives to UDMA 3 or 4.
PIO is for non DMA hard drives (usually under 2 GB).
MW-DMA is for CD-ROM devices.


HighPoint Technologies

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MrbreezeCommented:
In a nutshell. Tells you what to do with them but still not what they are
                             Mrbreeze
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